Screw locking means



Jan. 25, 1938.

M.H. REDMER SCREW LOCKING MEANS Filed Feb. 29, 1936 Patented Jan. 25, 1938.

UNITED STATES PATENT OFFICE SCREW LOCKING MEANS Martin n. Redmer, Chicago, m.

Application February 29, 1936, Serial No. 66,369

3 Claims.

My invention relates to screws. More particularly, my invention relates to an improved type of head fora screw whereby the screw may be threaded more readily into place without destroying the head by failure of the wrench or screw driver to align properly or to be fitted in the head.

As manufactured today, the type of screw fit the recess with considerable accuracy to prevent destruction of the recess by the sharp corners of the wrench. Moreover, an octagonal recess requiresremoval of material from that part of the head which considerably weakens the head. As the screw is driven into position and the head is coiintersunk, an octagonal recess provides no means for locking the screw in place to prevent it from accidentally becoming loose.

An object of my invention is to provide, therefore, an improved type of recess in thehead of a screw, which recess is preferably in the form of opposed sectors open at the edges of the head. Afurther object of my invention is to provide a recess in the head of a screw of the kind described, which does not weaken the construction of the head, and which further provides for engaging surfaces between the head and the key wrench that are in the most efiicient position to transmit the turning force. Accordingly, the screw may be threaded into position and tightened with minimum turning effort and without the danger of destroying the head.

A further object of my invention is to provide an improved typ of recess in the head of a screw that may receive a key or like locking member after the screw is tightly driven into position, which will prevent the screw from vibrating or otherwise working loose.

According to the present invention I further contemplate providing a novel key or locking device that may be inserted into a recess of a screw head and locked therein in a manner to bind against the part into which the screw is countersunk and thereby lock the screw in position.

In this connection, it is a still further object of the invention to provide a locking device of this type which can be readily placed in the recess in the screw head and, by slight tapping, caused to wedge itself against the walls of the recess and the part receiving the screwthe construction of the locking device-permitting, not only of simple use and low cost of manufacture, but also of ready removal in case it is desired to withdraw the screw.

Further objects of my invention will be apparent from the following detailed description taken 1 in connection with the accompanying drawing.

In the drawing:

Figure 1 is a perspective view of a screw having a recess in its head of the type embodying the present invention; 15

Fig. 2 is a planlview of the screw head;

Fig. 3 illustrates the type of key wrench that may be used;

Fig. 4 is a view of the end of the key wrench that fits into the recess in the head of the screw;

Fig; 5 is an edge view of a key or locking device adapted to be inserted in the recess of the screw head;

Fig. 6 is a plan view of this key .Vice;

Fig. 7 is a sectional view illustrating the screw driven into position and the head of the screw countersunk so as to show the manner in which this key or locking device prevents the screw from vibrating or otherwise working loose; and

Fig. 8 is a perspective view illustrating the manner in which atool may be used to remove this key or locking device when it is desired to remove this screw.

Referring now to the drawing, Fig. 1 illustrates a screw having a threaded shank and a head 2. Opposed sector-like recesses are provided in I the upper part of screw head 2. These opposed sector recesses are designated 3 and 4 and are joined at the center of the head, as indicated at 5, in a somewhat restricted manner due to this or locking desector formation, the center portion 5 being of such width as to permit insertion of a key wrench of corresponding shape. It is noted that sector recesses 3 and 4 extend outwardly to and are open at the edges 6 and 1 respectively of screw head 2. Becesses 3 and 4 provide walls 8 and 9 acting as engaging surfaces for the key wrench and being substantially radial so as to be somewhat transverse to the turning effort.

In the manufacture of the screw head 2, walls A 8 and 9 are cut at an angle to require but two milling operations in the formation of recesses 3 and-4. Although I do not necessarily Wish to be limited to an exact angle of cut for walls 8 and 9, I have found that by setting the milling cutters at 15 with respect to the horizontal, only two cutting operations are required to form these recesses 3 and 4. After the first cutting operation, the milling cutter may be indexed so that an opposite cut at may be performed to form the opposite walls. No material. is then left in the center of the recesses at the edges 6 and 1. One of the advantages, therefore, of cutting recesses 3 and 4 outwardly to the edges 6 and I resides in the simplicity of operation and inexpensive cost of production. Walls 8 and 9 remain in an angular position siifiicient to be somewhat transverse to the turning movement, and therefore, in the most efficient position when the key wrench is inserted to operate to thread the screw into locking position or to remove the same from locked position. Screws of this type are quite frequently used as keys to lock rotating parts together, such as is shown in Fig. 7.- This requires that the screw be driven into position as tightly as possible so that there is no opportunity for slippage between the rotating parts.

Moreover, it is essential that the screw remain locked to keep these operating parts keyed together. The formation of recesses 3 and 4 advantageously permit the use of a key-lock shown in Figs. 5 and 6. This key-lock, designated l2,

is of substantially the same cross section as recesses 3 and 4, but may be slightly curved so that when key-lock I2 is inserted in these recesses it may be tapped slightly to cause distortion and a wedging action with the walls 8 and 9 and the side wall of the part in which head 2 is countersunk. For example-in Fig."7 I have illustrated, say, a driving shaft i3 and a driven shaft l4. The screw is used as a key to lock parts I3 and I4 in driven relation. Head 2 is countersunk as is usual in these cases. Countersunk screws of this type may have an enlarged head 2, as shown in Fig. 1 of the drawing. It may also have a head of the same diameter as shank I, as is well understood and commonly used in the art. Irrespective of whether head/2 is enlarged, it will be noted that the arcuate edges l5 at each side of key-lock i2 will bind against wall It of the countersunk recesses in part l5. Key-lock I2 may be made of relatively soft material which will permit it to spread when tapped or pounded into recesses 3 and 4.

If key-lock I2 is made of relatively soft material it may be removed without difficulty. I

suggest providing an opening IT in the center where the material is constricted to conform to the center 5 where recesses 3 and 4 are joined as previously explained. Hole l1 'enables the placing of a punch l8 against key-lock l2 so that it may be readily split or torn apart, starting at the center where hole I1 is, when it is desired to remove key-lock l2 from the head 2. Any sharp instrument may be used instead of punch l8, or any means may be provided to initiate the quick removal of key-lock I 2 from recesses 3 and 4. On the other hand, it may not be necessary to provide hole I! to act as a means of starting the splitting or tearing action of the keylook at the center to enable removal of the sectors.

It will be noted that key-lock l2 provides a very simple and inexpensive key to lock the screw in position and effectively to prevent'vibration.

The arcuate edges P5 of this key-lock effectively grip the wall l6 when this key-lock is inserted in the recesses. Furthermore, key-lock I2 is permanent in its action and will remain in the recesses of head 2 until forcibly removed by means of a punch I8 or other sharp instrument.

Any type of key wrench such as I have designated and illustrated in Figs. 3 and 4 may be used to operate the screw. The lower end may be cut so that it will conform to thesize and shape of'recesses 3 and 4. This lower end 2| will then act as a key that will readily fit in these recesses in head 2 and securely engage walls 8 and 9 to drive the screw into position, permitting the turning effort to be efliciently transmitted without imposing too great a strain on head 2. Cutting recesses l3 and I4 in a manner to form opposite walls I and 8 at a relatively small angle, such forinstance as 15, not only minimizes the cutting operations but likewise leaves a maximum amount of material in the segments 22 and 23 to prevent destruction of the head by the key wrench. Moreover, it provides recesses of such conformation as to enable key wrench 20 to be readily inserted in the recesses although the screw may be located at an inconvenient point to the mechanic.

Without further elaboration, the foregoing will so fully explain the gist of my invention that others may, by applying current knowledge, readily adopt the same' for use under varying conditions 'of service, without eliminating certain features, which may properly be said to constitute the essential items of novelty involved, which items are intended to be defined and secured to me by the following claims.

cross section as that of said recesses adapted to be inserted therein and wedged against their walls and the wall of the member into which said screw is threaded to lock sai-d screw in position.

2. A screw comprising a threaded shank and a head having a substantially flat recess therein, said recess being open at ,the edge'of said head, and a locking member of substantially the same cross section as that of said recesses and wedged thcreinto in binding relation with the walls of said recess and the wall of the part in which said head is countersunk.

3. A screw to be countersunk in a work piece comprising a head and a .threaded shank, said head having substantially flat diametrically opposed reeesses joining each other in the center, said recesses being defined by side walls extending through the periphery of 'the head to provide an open end for each recess, and an initially- 

